CN101614681A - Micro-water content test system based on resonant cavity perturbation method - Google Patents

Abstract

The present invention relates to micro-water content test system based on resonant cavity perturbation method, this system has contained resonator cavity, frequency synthesizer, transceiver module, signal Processing, system design scheme technical field.System has proposed a kind of scheme of frequency precognition, this scheme adopts constant temperature with reference to crystal oscillator and phaselocked loop (PLL skill) art, can realize the output of less step frequency signal, primary controller can be according to measurement process control PLL, the VCO output frequency is set on the Frequency point that needs, thereby in Q value measuring process, do not need to carry out the measurement of frequency, this scheme can measure exactly resonator cavity have carry and the no-load situation under the Q value.This system has saved the module of frequency measurement, greatly reduces the technical difficulty of system, has reduced cost.

Description

Micro-water content test system based on resonant cavity perturbation method

One, technical field

The present invention relates to micro-water content test system based on resonant cavity perturbation method, this system has contained resonator cavity, frequency synthesizer, transceiver module, signal Processing, system design scheme technical field.Micro-water content is based on the perturbation of resonator cavity in the Cavity Perturbation Method measurement turbine oil, and promptly the resonance frequency of resonator cavity with dielectric change in dielectric constant in the chamber this principle of skew takes place.This system can be applicable to micro-water contents such as oil, water conservancy and measures.

Two, background technology

Country's metering technology normalized is defined as moisture to the content of water in solid and the liquid substance.Moisture is that solid and liquid substance need one of most important parameters of understanding in production, transportation, storage, transaction with during handling.What of moisture in solid and the liquid substance, to Substance Properties, the storage of material and processability, the output of product and quality, the transportation of product etc. all has material impact, so the measurement of moisture and control have great economy and technological value.Utilizing microwave that material is carried out the moisture measurement is a kind of important method in the modern surveying, and obtains widespread use in numerous industries.

In many industrial and agricultural production processes, the water percentage of some material has very important influence to performance, quality and the production efficiency of product.In some occasion, require the water percentage of online nondestructive measurement material, and then realize entire production process is carried out line closed loop control, this just has higher requirement to the hygrometric method.

At first, the hygrometric method should be certain lossless detection method, and promptly in testing process, the structure and composition of measured object can not destroyed.Secondly, pick-up unit should be able to be realized on-line measurement, so that survey water process and production, transportation are not mutually exclusive.Detection mode preferably adopts contactless, so that the hygrometric device adapts to production run.

The existing hygrometric principle that can realize online nondestructive measurement, its measurement result major part is subjected to the influence of tested material density.。Material is in processing, in the course of conveying generally speaking, and its density can change, as bulk grain etc.; Even its density itself also is to produce one of required data sometimes, as pipe tobacco etc.Will with the measuring method of routine satisfy harmless, in real time, measure under the condition such as noncontact in, accomplishing that measurement result and density have nothing to do maybe can carry out the density correction to the moisture reading, just must improve measuring principle in the past.

With the based on resonant cavity perturbation method measuring method time, in existing scheme, all need to measure the frequency and the power of pumping signal, high precision frequency measurement technical difficulty is big, native system adopts phaselocked loop (PLL) technology to realize the emission signal frequency precognition, this scheme can be saved the frequency measurement part, simplify system schema greatly, reduced cost.

Three, summary of the invention

The objective of the invention is to realize a micro-water content test system based on resonant cavity perturbation method, based on the perturbation of resonator cavity, promptly this principle of skew takes place with dielectric change in dielectric constant in the chamber in the resonance frequency of resonator cavity.Under uniform temp, pressure, because the specific inductive capacity of steam turbine oil and water is different, the specific inductive capacity of different its mixed solutions of water cut is also just different in the turbine oil, when the steam turbine oil that contains moisture passes through microwave cavity, its resonance frequency will be offset, and side-play amount is different and different with the water percentage in the turbine oil, therefore can determine what of micro-water content in the steam turbine oil by the side-play amount of measuring the resonator cavity resonance frequency.Native system is filled the resonant frequency point and the Q value of resonator cavity down, relative dielectric Changshu of anhydrous oil by measuring anhydrous oil; Using the same method to record the relative dielectric Changshu that contains little water oil, and contrast anhydrous oil and little water oil phase can obtain the micro-water content of oil to dielectric Changshu and in conjunction with the lumped parameter of resonator cavity.Native system can be applied in the micro-water content measurement in petroleum industry and water conservancy field.

Resonant frequency point and Q value that the Resonant-cavity Method test micro-water content that native system adopts need be tested resonator cavity, traditional way is to control the signal of voltage-controlled oscillator (VCO) output certain frequency by a DC voltage, with this signal de-energisation resonator cavity, owing to have uncertain relation between VCO control voltage and the output frequency, can not obtain accurate VCO frequency by control voltage, native system will be tested the power and the frequency of resonator cavity coupling output terminal output signal, measurement for power can realize by power detector, if micro-water content is ten thousand in the turbine oil/or when lower, then to arrive hundreds of hertz even tens hertz, increase technical difficulty the measuring accuracy of VCO output signal frequency.System has proposed a kind of scheme of frequency precognition, this scheme adopts constant temperature with reference to crystal oscillator and phaselocked loop (PLL skill) art, can realize the output of less step frequency signal, primary controller can be according to measurement process control PLL, the VCO output frequency is set on the Frequency point that needs, thereby in Q value measuring process, do not need to carry out the measurement of frequency, this scheme can measure exactly resonator cavity have carry and the no-load situation under the Q value.This system has saved the module of frequency measurement, greatly reduces the technical difficulty of system, has reduced cost.

Four, description of drawings

Explain the present invention with reference to the accompanying drawings, wherein

Fig. 1 micro-water content test system based on resonant cavity perturbation method scheme block diagram

Fig. 2 micro-water content measuring accuracy and frequency resolution relation curve

Fig. 3 micro-water content test system based on resonant cavity perturbation method workflow

Five, embodiment

5.1 micro-water content test system based on resonant cavity perturbation method overall plan

But, the parameters such as frequency of micro-water content test system based on resonant cavity perturbation method are carried out preferably according to volume, industry applying frequency and development of electronic technology situation to being applicable to the solid resonator cavity.According to the frequency assignation of Wireless Management Committee, the frequency ratio of 2.4GHz is used in this problem.

The micro-water content test system based on resonant cavity perturbation method scheme as shown in Figure 1, this system comprises single port resonator cavity 1, Waveguide-microbelt excessive device 2, is bridge 3, VCO voltage controlled oscillator (HMC385) 4, PLL chip (AD4106) 5, constant-temperature crystal oscillator (100MHz) 6, wave detector (AD8318) 7, amplifier (HMC385) 8, ADC (AD7656) 9, FPGA (XC3S400) 10, DSP (TMS320F2812) 11 and pressure transducer, temperature sensor and the display part of going in ring.System's each several part implementation will be done concrete introduction in the back.

5.2 research method and technological approaches

When utilizing microwave cavity to measure material moisture, microwave cavity has higher figure of merit value, makes to detect to have very high resolving power and precision; Because microwave cavity is a narrow-band pass filter, available resonance frequency deviation value records associated arguments again, and itself just has excellent shielding effect the metallic cavity of ground connection, so microwave cavity has well anti-interference and antistatic interference performance; Simultaneously can realize noncontacting measurement again, minimizing or elimination are because the measuring error that contact measurement brings; For lossy tested material, by the resonance frequency of measurement resonator cavity and the variation of quality factor, can record the specific inductive capacity and the decay factor of moisture simultaneously, utilize the ratio of the two to eliminate the influence of density, thereby realize and density independent microwave cavity moisture measurement measurement result.

For the material of tested moisture such as powder, particle, be actually the potpourri of air and measured matter, its effective dielectric constant is relevant with density.With function representation be:

$\mathrm{\ϵ}={[({\mathrm{\ϵ}}_2^{1/3}-{\mathrm{\ϵ}}_1^{1/3})V+{\mathrm{\ϵ}}_1^{1/3}]}^3---\left(1\right)$

Wherein V is the number percent of the shared volume of measured matter.ε ₁Be dielectric constant of air, ε ₂Specific inductive capacity for measured matter.

Microwave moisture measurement is actually that effective composite dielectric constant by material carries out, therefore must adopt the density control measure or with density independent means of testing (as the dual sensor method) or with density independent algorithm.First kind of operability is relatively poor, second kind of complexity that increases system.The third way is the method that widely adopts in recent years, comprises various and irrelevant Operator Method of density and the method for setting up the potpourri complex permittivity model of tested material.

1 with the irrelevant Operator Method of density

Realize that the main means with the irrelevant Operator Method of density are to seek an intermediate function that not influenced by density and can set up relational expression with moisture, this function obtains definite function of moisture then as " with the irrelevant operator of density " with the method for linear regression.As A/ Ф, (ε '-1)/ε ", ε "/[ε ' (α ₁ε '-ε ")] etc. (wherein A is the amplitude fading factor, and Ф is the phase shifts factor).

This method is used a sensor, detects two resonance parameters (resonance frequency and quality factor) simultaneously.System constitutes simpler.

2 solid-liquids-gas three-phase mixture complex permittivity model

No matter be adopt the density control measure or with density independent means of testing (as the dual sensor method), still adopt and the irrelevant Operator Method of density, when obtaining the moisture equation, all to use homing method, just will do a large amount of experiments and obtain some parameter in the equation by handling experimental data.This has very big influence to measuring accuracy.The reason of using homing method is---liquid---gas three-phase mixture complex permittivity model of not setting up complete consolidating.

This model can be used as the connection of mixture specific inductive capacity and material density and moisture thereof, finally derives moisture and decay factor and phase factor, or the equation of moisture and resonance frequency and quality factor.

Because the resonator that the front was mentioned is as the advantage of sensor and the inferior position of free space measuring method, research is the relation of moisture and resonance frequency and quality factor here.

Water-containing materials can be regarded as by the water of the material of solid, liquid and the three kinds of materials such as air in the intermediate gap and mix.In this three's the mixing, material and water almost are to mix completely, have not both had independent aqueous water also not have the material of pure drying.Wherein can separate be exactly granular, cotton-shaped or sheet material is piled up air in the slit.So at first only consider tested material molecule and the hydrone electromagnetic property in electromagnetic field.Consider that the mixing of material molecule and hydrone meets the compound system of particle, so can use the Maxwell-Garnett theory to analyze.

A Maxwell-Garnett theory

The electromagnetic property of the theoretical main research potpourri of Maxwell-Garnett is to being uniform-distribution with the compound system of spheric grain at random in the matrix, wherein filler particles is thought hydrone, and its electromagnetic parameter is ε _i, μ _i, the volume dutycycle is f, wherein matrix is that material molecule volume dutycycle is 1-f.The matrix electromagnetic parameter is ε _m, μ _mSuppose that compound system equivalent electric magnetic parameter is ε _Eff, μ _EffHere only complex permittivity is discussed.Compound system under the alternating electromagnetism field action, the average electric field＜E of whole system〉can be expressed as

<E>＝f<E _i>+(1-f)<E _m>????????????????????????????(2)

The average electrical displacement vector of whole system is

<D>＝fε _i<D _i>+(1-f)ε _m<D _m>??????????????????????(3)

Be defined as according to the effective dielectric constant of medium at random

D＝ε _effE

Can get

${\mathrm{\&epsiv;}}_{\mathrm{eff}}=\frac{<D>}{<E>}=\frac{{\mathrm{f\&epsiv;}}_i<E_i>+(1-f){\mathrm{\&epsiv;}}_m<E_m>}{f<E_i>+(1-f)<E_m>}---\left(4\right)$

Have again

$<E_i>=\frac{1}{3}[\frac{{\mathrm{\&epsiv;}}_m}{L_{i1}{\mathrm{\&epsiv;}}_i+(1-L_{i1}){\mathrm{\&epsiv;}}_m}+\frac{2{\mathrm{\&epsiv;}}_m}{L_{i2}{\mathrm{\&epsiv;}}_i+(1-L_{i2}){\mathrm{\&epsiv;}}_m}]---\left(5\right)$

Here L _I1, L _I2And L _I3Be isotropy particle polarizability tnesor,

$L_i=\left(\begin{array}{ccc}{L}_{i1}& & \\ & L_{i2}& \\ & & L_{i3}\end{array}\right)---\left(6\right)$

To semiaxis is a, b, and the ellipsoid particle of c has

$L_{i1}=\frac{\mathrm{abc}}{4\mathrm{\&pi;}}{\&Integral;}_0^{\&infin;}\frac{\mathrm{ds}}{(s-a^2)R_s}$

$L_{i2}=\frac{\mathrm{abc}}{4\mathrm{\&pi;}}{\&Integral;}_0^{\&infin;}\frac{\mathrm{ds}}{(s-b^2)R_s}$

$L_{i3}=\frac{\mathrm{abc}}{4\mathrm{\&pi;}}{\&Integral;}_0^{\&infin;}\frac{\mathrm{ds}}{(s-c^2)R_s}$

${\mathrm{<figure-callout\; id="2"\; label="R\; s"\; filenames="A2009101477550015H1.png,A2009101477550016H1.png"\; state="\{\{state\}\}">R</figure-callout>}}_s^{}=(s-a^2)(s-b^2)(s-c^2)$

For spheroidal particle, a=b=c then has L _I1=L _I2=L _I3=1/3

With D=ε _EffE and formula (5) substitution formula (4) then has

${\mathrm{\&epsiv;}}_{\mathrm{eff}}={\mathrm{\&epsiv;}}_m+3f{\mathrm{\&epsiv;}}_m\frac{{\mathrm{\&epsiv;}}_i-{\mathrm{\&epsiv;}}_m}{{\mathrm{\&epsiv;}}_i+2{\mathrm{\&epsiv;}}_m}---\left(7\right)$

Classical Maxwell-Garnett formula has been considered the polarization characteristic of each particle scatterer, and its formula is

${\mathrm{\&epsiv;}}_{\mathrm{eff}}={\mathrm{\&epsiv;}}_m+3f{\mathrm{\&epsiv;}}_m\frac{{\mathrm{\&epsiv;}}_i-{\mathrm{\&epsiv;}}_m}{{\mathrm{\&epsiv;}}_i+2{\mathrm{\&epsiv;}}_m-f({\mathrm{\&epsiv;}}_i-{\mathrm{\&epsiv;}}_m)}---\left(8\right)$

Promptly

$\frac{{\mathrm{\&epsiv;}}_{\mathrm{eff}}-{\mathrm{\&epsiv;}}_m}{{\mathrm{\&epsiv;}}_{\mathrm{eff}}+2{\mathrm{\&epsiv;}}_m}=f\frac{{\mathrm{\&epsiv;}}_i-{\mathrm{\&epsiv;}}_m}{{\mathrm{\&epsiv;}}_i+2{\mathrm{\&epsiv;}}_m}---\left(9\right)$

According to the duality principle of electromagnetic theory, can get equally

$\frac{{\mathrm{\&mu;}}_{\mathrm{eff}}-{\mathrm{\&mu;}}_m}{{\mathrm{\&mu;}}_{\mathrm{eff}}+2{\mathrm{\&mu;}}_m}=f\frac{{\mathrm{\&mu;}}_i-{\mathrm{\&mu;}}_m}{{\mathrm{\&mu;}}_i+2{\mathrm{\&mu;}}_m}---\left(10\right)$

The formula form that is suitable for various systems is

$\frac{{\mathrm{\&epsiv;}}_{\mathrm{eff}}-{\mathrm{\&epsiv;}}_m}{{\mathrm{\&epsiv;}}_{\mathrm{eff}}+(D-1){\mathrm{\&epsiv;}}_m}=f\frac{{\mathrm{\&epsiv;}}_i-{\mathrm{\&epsiv;}}_m}{{\mathrm{\&epsiv;}}_i+(D-1)2{\mathrm{\&epsiv;}}_m}---\left(11\right)$

$\frac{{\mathrm{\&mu;}}_{\mathrm{eff}}-{\mathrm{\&mu;}}_m}{{\mathrm{\&mu;}}_{\mathrm{eff}}+(D-1){\mathrm{\&mu;}}_m}=f\frac{{\mathrm{\&mu;}}_i-{\mathrm{\&mu;}}_m}{{\mathrm{\&mu;}}_i+(D-1)2{\mathrm{\&mu;}}_m}---\left(12\right)$

In the formula, f is the volumn concentration of particle, and D is the dimension of applicable system.Usually the system of discussing all is three-dimensional, and D gets 3, then is form commonly used.

The Maxwell-Garnett theory of b conductive particles dispersed system

To the conductive particles dispersed system, need to consider that each component of material is to the interaction between electromagnetic response and component.If the conductive particles conductivity of disperseing is σ, its complex permittivity is

ε _i＝ε′+jσ/ω????????????????????????????(13)

Then the equivalent complex permittivity of compound system can be calculated by the Maxwell-Garnett formula, promptly

$\frac{{{\mathrm{\&epsiv;}}^{\&prime;}}_{\mathrm{eff}}+j{\mathrm{\&sigma;}}_{\mathrm{eff}}/\mathrm{\&omega;}-{\mathrm{\&epsiv;}}_m}{{{\mathrm{\&epsiv;}}^{\&prime;}}_{\mathrm{eff}}+j{\mathrm{\&sigma;}}_{\mathrm{eff}}/\mathrm{\&omega;}+2{\mathrm{\&epsiv;}}_m}=f\frac{{{\mathrm{\&epsiv;}}^{\&prime;}}_i+\mathrm{j\&sigma;}/\mathrm{\&omega;}-{\mathrm{\&epsiv;}}_m}{{{\mathrm{\&epsiv;}}^{\&prime;}}_i+\mathrm{j\&sigma;}/\mathrm{\&omega;}+2{\mathrm{\&epsiv;}}_m}---\left(14\right)$

When the volume dutycycle of conductive particles was very little, equivalent conductivity was expressed as

${\mathrm{\&sigma;}}_{\mathrm{eff}}=\frac{{9\mathrm{\&sigma;}}_{\mathrm{<figure-callout\; id="2"\; label="m"\; filenames="A2009101477550015H1.png,A2009101477550016H1.png"\; state="\{\{state\}\}">m</figure-callout>}}^2\mathrm{f\&sigma;}}{{({{\mathrm{\&epsiv;}}^{\&prime;}}_m+2{\mathrm{\&epsiv;}}_m)}^2+\frac{{\mathrm{\&sigma;}}^2}{{\mathrm{\&omega;}}^2}}---\left(15\right)$

In addition, when propagating, frequency electromagnetic waves can not penetrate into the inside of particle fully in metallic particles, only concentrate in one deck of very thin surface, its thickness is expressed as skin depth δ, skin depth δ is relevant with particle diameter, the conductivity of filler particles, and there is the frequency dispersion effect, very big to the eddy current loss influence.Mahan during to the influencing of magnetic polarization coefficient, has introduced A (a, σ, ε in processing variation magnetic field in the Bruggenman formula _i, ω),

$A(a,\mathrm{\&sigma;},{\mathrm{\&epsiv;}}_i,\mathrm{\&omega;})=\frac{2[\mathrm{ka}\cos \left(\mathrm{ka}\right)-\sin \left(\mathrm{ka}\right)]}{\sin \left(\mathrm{ka}\right)-\mathrm{ka}\cos \left(\mathrm{ka}\right)-k^2{a}^2\sin \left(\mathrm{ka}\right)}---\left(16\right)$

In the formula, a, σ, ε _iBe respectively particle diameter, complex permittivity and the conductivity of adsorbent, ω represents frequency.Wave number k is the amount relevant with the particle electromagnetic property.If particle is a conductor, wave number can be expressed as

$k=\frac{1+i}{\mathrm{\&delta;}}=(1+i){\left(\frac{{\mathrm{\&sigma;\&omega;\&mu;}}_k}{{2\mathrm{\&epsiv;}}_0{c}^2}\right)}^{1/2}---\left(17\right)$

Obvious μ at this moment _i=A (a, σ, ε _i, ω) μ _IstaticRevised Bruggenman formula can explain well that the conducting sphere particle composites is the variation of equivalent complex permeability with electromagnetic field, and thinks that this correction has taken into full account the effect of eddy current loss.Thus, in classical Maxwell-Garnett formula, introduce this formula, formula further is deformed into

$\frac{{\mathrm{\&epsiv;}}_{\mathrm{eff}}-{\mathrm{\&epsiv;}}_m}{{\mathrm{\&epsiv;}}_{\mathrm{eff}}+2{\mathrm{\&epsiv;}}_m}=f\frac{A(a,\mathrm{\&sigma;},{\mathrm{\&epsiv;}}_i,\mathrm{\&omega;}){\mathrm{\&epsiv;}}_i-{\mathrm{\&epsiv;}}_m}{A(a,\mathrm{\&sigma;},{\mathrm{\&epsiv;}}_i,\mathrm{\&omega;}){\mathrm{\&epsiv;}}_i+2{\mathrm{\&epsiv;}}_m}---\left(18\right)$

$\frac{{\mathrm{\&mu;}}_{\mathrm{eff}}-{\mathrm{\&mu;}}_m}{{\mathrm{\&mu;}}_{\mathrm{eff}}+2{\mathrm{\&mu;}}_m}=f\frac{A(a,\mathrm{\&sigma;},{\mathrm{\&epsiv;}}_i,\mathrm{\&omega;}){\mathrm{\&mu;}}_i-{\mathrm{\&mu;}}_m}{A(a,\mathrm{\&sigma;},{\mathrm{\&epsiv;}}_i,\mathrm{\&omega;}){\mathrm{\&mu;}}_i+2{\mathrm{\&mu;}}_m}---\left(19\right)$

These two formulas have been done certain improvement to the characteristics of conductive particles to classical Maxwell-Garnett formula from two angle pins respectively:

$\frac{{{\mathrm{\&epsiv;}}^{\&prime;}}_{\mathrm{eff}}+j{\mathrm{\&sigma;}}_{\mathrm{eff}}/\mathrm{\&omega;}-{\mathrm{\&epsiv;}}_m}{{{\mathrm{\&epsiv;}}^{\&prime;}}_{\mathrm{eff}}+j{\mathrm{\&sigma;}}_{\mathrm{eff}}/\mathrm{\&omega;}+2{\mathrm{\&epsiv;}}_m}=f\frac{{{\mathrm{\&epsiv;}}^{\&prime;}}_i+\mathrm{j\&sigma;}/\mathrm{\&omega;}-{\mathrm{\&epsiv;}}_m}{{{\mathrm{\&epsiv;}}^{\&prime;}}_i+\mathrm{j\&sigma;}/\mathrm{\&omega;}+2{\mathrm{\&epsiv;}}_m}---\left(20\right)$

$\frac{{\mathrm{\&epsiv;}}_{\mathrm{eff}}-{\mathrm{\&epsiv;}}_m}{{\mathrm{\&epsiv;}}_{\mathrm{eff}}+2{\mathrm{\&epsiv;}}_m}=f\frac{A(a,\mathrm{\&sigma;},{\mathrm{\&epsiv;}}_i,\mathrm{\&omega;}){\mathrm{\&epsiv;}}_i-{\mathrm{\&epsiv;}}_m}{A(a,\mathrm{\&sigma;},{\mathrm{\&epsiv;}}_i,\mathrm{\&omega;}){\mathrm{\&epsiv;}}_i+2{\mathrm{\&epsiv;}}_m}---\left(21\right)$

C is based on the potpourri complex permittivity model of volume ratio

Our original idea is solid---liquid---gas three-phase mixture complex permittivity model of research.Above two trifles studied two kinds of mixed electromagnetic propertys of particle, do not comprise this part material of air.Therefore at first with the air separation in the potpourri.

Consider water and mixtures of materials electromagnetic property earlier, can get according to last joint formula

${\mathrm{\&epsiv;}}^{*}=\frac{1}{{\mathrm{\&upsi;}}_D+{\mathrm{\&upsi;}}_W}({\mathrm{\&upsi;}}_D{\mathrm{\&epsiv;}}_D^{*}+{\mathrm{\&upsi;}}_W+{\mathrm{\&epsiv;}}_W^{*}\left(k^2{a}^2\sin \left(\mathrm{ka}\right)\right)+\frac{2{\mathrm{\&sigma;}}_{\mathrm{eff}}\mathrm{ka}\sin \left(\mathrm{ka}\right)}{\sin \left(\mathrm{ka}\right)-\mathrm{ka}\cos \left(\mathrm{ka}\right)})---\left(22\right)$

According to wave number definition and hydrone electromagnetic property, can be similar to k ²a ²Sin (ka)=1, σ _Eff≈ 0.2 * 10 ^-7With formula (22) abbreviation be

${\mathrm{\&epsiv;}}^{*}=\frac{1}{{\mathrm{\&upsi;}}_D+{\mathrm{\&upsi;}}_W}({\mathrm{\&upsi;}}_D{\mathrm{\&epsiv;}}_D^{*}+{\mathrm{\&upsi;}}_W{\mathrm{\&epsiv;}}_W^{*})---\left(23\right)$

Formula (23) can be regarded as the specific inductive capacity expression formula based on the material particles potpourri of volume ratio, generally uses this formula will cause than mistake, and the main cause that can use like this in this example is the equivalent conductivity σ of water _EffEnough little.

The air that separates from potpourri is at first given and consideration in the lump, and the volume of establishing air, water and dried material is respectively υ _A, υ _WAnd υ _D, subscript W and D represent water and dried material respectively, and cumulative volume V=υ _A+ υ _W+ υ _DLike this, the aqueous mixture complex permittivity can be expressed as follows:

${\mathrm{\&epsiv;}}^{*}=\frac{1}{V}({\mathrm{\&upsi;}}_A{\mathrm{\&epsiv;}}_A^{*}+{\mathrm{\&upsi;}}_D{\mathrm{\&epsiv;}}_D^{*}+{\mathrm{\&upsi;}}_W{\mathrm{\&epsiv;}}_W^{*})---\left(24\right)$

Obtain thus promptly based on the potpourri complex permittivity model of volume ratio, it with the volume ratio of each composition in the potpourri as the weights of its specific inductive capacity and add and form.

The density separation method of d sensor resonant parameter

Include material moisture and two parameters of material density simultaneously in---exactly because Gu liquid---gas three-phase mixture complex permittivity model, so the moisture measurement process can be subjected to the influence of density.Ensuing purpose is separation of material density and two parameters of moisture from this model.

According to the model of last joint, has certain volume and moisture material can be approximately the potpourri of being made up of three parts: the air of (1) certain volume; (2) dried material of certain volume; (3) pure water of certain volume.The complex permittivity of mixture just can be expressed as follows with the complex permittivity and the volume ratio weighting of three parts like this:

${\mathrm{\&epsiv;}}^{*}=\frac{v_A}{V}+\frac{m_D}{V{\mathrm{\&rho;}}_D}{{\mathrm{\&epsiv;}}_D}^{*}+\frac{m_W}{V{\mathrm{\&rho;}}_W}{{\mathrm{\&epsiv;}}_W}^{*}---\left(25\right)$

υ wherein _ABe the volume of air in the potpourri, subscript D and W refer to dried material and water respectively, and ρ is a material density.Spent material density and material moisture replace quality and the volume correlated variables in the former formula to get:

${\mathrm{\&epsiv;}}^{*}=\frac{v_A}{V}+\mathrm{\&rho;}(1-\mathrm{\&psi;})\frac{{\mathrm{\&epsiv;}}_D^{*}}{{\mathrm{\&rho;}}_D}+\mathrm{\&rho;\&psi;}\frac{{\mathrm{\&epsiv;}}_W^{*}}{{\mathrm{\&rho;}}_W}---\left(26\right)$

ε * is launched to become energy storage factor ε ' and dissipation factor ε " form be:

${\mathrm{\&epsiv;}}^{\&prime;}=\frac{v_A}{V}+\mathrm{\&rho;}(1-\mathrm{\&psi;})\frac{{{\mathrm{\&epsiv;}}^{\&prime;}}_D}{{\mathrm{\&rho;}}_D}+\mathrm{\&rho;\&psi;}\frac{{{\mathrm{\&epsiv;}}^{\&prime;}}_W}{{\mathrm{\&rho;}}_W}---\left(27\right)$

${\mathrm{\&epsiv;}}^{\&prime;\&prime;}=\mathrm{\&rho;}(1-\mathrm{\&psi;})\frac{{{\mathrm{\&epsiv;}}^{\&prime;\&prime;}}_D}{{\mathrm{\&rho;}}_D}+\mathrm{\&rho;\&psi;}\frac{{{\mathrm{\&epsiv;}}^{\&prime;\&prime;}}_W}{{\mathrm{\&rho;}}_W}---\left(28\right)$

Remove outside material density ρ and the moisture ψ υ in formula (27) and the formula (28) _AWith V also be variable, it also should be expressed as the function of ρ and ψ.According to V=υ _A+ υ _W+ υ _DFurther derive following formula:

$\frac{v_A}{V}=1-\frac{\mathrm{\&rho;}}{{\mathrm{\&rho;}}_D}(1-\mathrm{\&psi;})-\frac{\mathrm{\&rho;}}{{\mathrm{\&rho;}}_D}\mathrm{\&psi;}---\left(29\right)$

Take back formula (27) again, can obtain:

${\mathrm{\&epsiv;}}^{\&prime;}=1+\mathrm{\&rho;}(1-\mathrm{\&psi;})\frac{{{\mathrm{\&epsiv;}}^{\&prime;}}_D-1}{{\mathrm{\&rho;}}_D}+\mathrm{\&rho;\&psi;}\frac{{{\mathrm{\&epsiv;}}^{\&prime;}}_W-1}{{\mathrm{\&rho;}}_W}---\left(30\right)$

Can allow 4 known variables appear in two equations now, so just can obtain material moisture ψ and material density ρ expression formula about the material specific inductive capacity energy storage factor and dissipation factor.Moisture with material in two expression formulas thoroughly separates with density, and concrete form is as follows:

$\mathrm{\&psi;}=\frac{\frac{{{\mathrm{\&epsiv;}}^{\&prime;}}_D-1}{{\mathrm{\&rho;}}_D}\&CenterDot;{\mathrm{\&epsiv;}}^{\&prime;\&prime;}-\frac{{{\mathrm{\&epsiv;}}^{\&prime;\&prime;}}_D}{{\mathrm{\&rho;}}_D}\&CenterDot;({\mathrm{\&epsiv;}}^{\&prime;}-1)}{({\mathrm{\&epsiv;}}^{\&prime;}-1)(\frac{{{\mathrm{\&epsiv;}}^{\&prime;\&prime;}}_W}{{\mathrm{\&rho;}}_W}-\frac{{{\mathrm{\&epsiv;}}^{\&prime;\&prime;}}_D}{{\mathrm{\&rho;}}_D})-{\mathrm{\&epsiv;}}^{\&prime;\&prime;}(\frac{{{\mathrm{\&epsiv;}}^{\&prime;}}_W-1}{{\mathrm{\&rho;}}_W}-\frac{{{\mathrm{\&epsiv;}}^{\&prime;}}_D-1}{{\mathrm{\&rho;}}_D})}---\left(31\right)$

$\mathrm{\&rho;}=\frac{{\mathrm{\&epsiv;}}^{\&prime;\&prime;}}{\frac{{{\mathrm{\&epsiv;}}^{\&prime;\&prime;}}_D}{{\mathrm{\&rho;}}_D}+\frac{\frac{{{\mathrm{\&epsiv;}}^{\&prime;}}_D-1}{{\mathrm{\&rho;}}_D}\&CenterDot;{\mathrm{\&epsiv;}}^{\&prime;\&prime;}-\frac{{{\mathrm{\&epsiv;}}^{\&prime;\&prime;}}_D}{{\mathrm{\&rho;}}_D}\&CenterDot;({\mathrm{\&epsiv;}}^{\&prime;}-1)}{({\mathrm{\&epsiv;}}^{\&prime;}-1)(\frac{{{\mathrm{\&epsiv;}}^{\&prime;\&prime;}}_W}{{\mathrm{\&rho;}}_W}-\frac{{{\mathrm{\&epsiv;}}^{\&prime;\&prime;}}_D}{{\mathrm{\&rho;}}_D})-{\mathrm{\&epsiv;}}^{\&prime;\&prime;}(\frac{{{\mathrm{\&epsiv;}}^{\&prime;}}_W-1}{{\mathrm{\&rho;}}_W}-\frac{{{\mathrm{\&epsiv;}}^{\&prime;}}_D-1}{{\mathrm{\&rho;}}_D})}(\frac{{{\mathrm{\&epsiv;}}^{\&prime;\&prime;}}_W}{{\mathrm{\&rho;}}_W}-\frac{{{\mathrm{\&epsiv;}}^{\&prime;\&prime;}}_D}{{\mathrm{\&rho;}}_D})}---\left(32\right)$

Further formula (31) and formula (32) abbreviation are got:

$\mathrm{\&psi;}=\frac{a{\mathrm{\&epsiv;}}^{\&prime;\&prime;}-b{\mathrm{\&epsiv;}}^{\&prime;}-b}{c{\mathrm{\&epsiv;}}^{\&prime;}-c-d{\mathrm{\&epsiv;}}^{\&prime;\&prime;}}$

$\mathrm{\&rho;}=\frac{{\mathrm{\&epsiv;}}^{\&prime;}}{b+\frac{{\mathrm{a\&epsiv;}}^{\&prime;\&prime;}-{\mathrm{b\&epsiv;}}^{\&prime;}-b}{{\mathrm{c\&epsiv;}}^{\&prime;}-c-d{\mathrm{\&epsiv;}}^{\&prime;\&prime;}}d}$

Wherein,

$a=\frac{{{\mathrm{\&epsiv;}}^{\&prime;}}_D-1}{{\mathrm{\&rho;}}_D}$

$b=\frac{{{\mathrm{\&epsiv;}}^{\&prime;\&prime;}}_D}{{\mathrm{\&rho;}}_D}$

$c=\frac{{{\mathrm{\&epsiv;}}^{\&prime;\&prime;}}_W}{{\mathrm{\&rho;}}_W}-\frac{{{\mathrm{\&epsiv;}}^{\&prime;\&prime;}}_D}{{\mathrm{\&rho;}}_D}$

$d=\frac{{{\mathrm{\&epsiv;}}^{\&prime;}}_W-1}{{\mathrm{\&rho;}}_W}-\frac{{{\mathrm{\&epsiv;}}^{\&prime;}}_D-1}{{\mathrm{\&rho;}}_D}$

If material determines, a so, b, c, d are constant.Therefore the moisture of tested material and density are respectively the function about the energy storage factor and dissipation factor.Like this, as long as just can set up the funtcional relationship of material moisture and sensor parameters in conjunction with the relational expression of material specific inductive capacity and sensor resonance parameter, and this funtcional relationship and material density have nothing to do, and realized and density independent measurement.

Gu---liquid---gas three-phase mixture complex permittivity model can combine with multiple moisture measuring method.Any measuring method as long as the parameter of its detection is the energy storage factor and the dissipation factor of specific inductive capacity, all can be used the model here, thereby sets up the final relation that detects parameter and material moisture.

E and density independent material moisture are measured equation

The measurement of material moisture is actually to be finished by the dielectric property of measuring material.By this bridge of material specific inductive capacity, set up on the one hand the relation of itself and material moisture, set up the relation of variable in itself and the measuring method on the other hand, finally can set up whole measuring process.

For resonator cavity, can obtain following system of equations:

$f=\frac{1}{2\mathrm{\&pi;}}\&CenterDot;\frac{1}{\sqrt{L({\mathrm{<figure-callout\; id="0"\; label="C"\; filenames="A2009101477550016H1.png"\; state="\{\{state\}\}">C</figure-callout>}}_0+C_1{C}_2\frac{C_2({\mathrm{\&epsiv;}}^{\&prime;2}+{\mathrm{\&epsiv;}}^{\&prime;\&prime;2})+{\mathrm{<figure-callout\; id="1"\; label="C"\; filenames="A2009101477550016H1.png"\; state="\{\{state\}\}">C</figure-callout>}}_1{\mathrm{\&epsiv;}}^{\&prime;}}{{{\mathrm{<figure-callout\; id="2"\; label="C"\; filenames="A2009101477550015H1.png,A2009101477550016H1.png"\; state="\{\{state\}\}">C</figure-callout>}}_2}^2({\mathrm{\&epsiv;}}^{\&prime;2}+{\mathrm{\&epsiv;}}^{\&prime;\&prime;2})+2C_1{\mathrm{<figure-callout\; id="2"\; label="C"\; filenames="A2009101477550015H1.png,A2009101477550016H1.png"\; state="\{\{state\}\}">C</figure-callout>}}_2{\mathrm{\&epsiv;}}^{\&prime;}+{{\mathrm{<figure-callout\; id="1"\; label="C"\; filenames="A2009101477550016H1.png"\; state="\{\{state\}\}">C</figure-callout>}}_1}^2})}}---\left(33\right)$

$\frac{1}{Q}=\frac{1}{2\mathrm{\&pi;}{\mathrm{<figure-callout\; id="0"\; label="f"\; filenames="A2009101477550016H1.png"\; state="\{\{state\}\}">f</figure-callout>}}_0}\&CenterDot;\frac{G+2\mathrm{\&pi;<figure-callout\; id="1"\; label="f\; C"\; filenames="A2009101477550016H1.png"\; state="\{\{state\}\}">f</figure-callout>}{C_{}}^{}{{}_1}^2{\mathrm{<figure-callout\; id="2"\; label="C"\; filenames="A2009101477550015H1.png,A2009101477550016H1.png"\; state="\{\{state\}\}">C</figure-callout>}}_2\frac{{\mathrm{\&epsiv;}}^{\&prime;\&prime;}}{{{\mathrm{<figure-callout\; id="2"\; label="C"\; filenames="A2009101477550015H1.png,A2009101477550016H1.png"\; state="\{\{state\}\}">C</figure-callout>}}_2}^2({\mathrm{\&epsiv;}}^{\&prime;2}+{\mathrm{\&epsiv;}}^{\&prime;\&prime;2})+2C_1{\mathrm{<figure-callout\; id="2"\; label="C"\; filenames="A2009101477550015H1.png,A2009101477550016H1.png"\; state="\{\{state\}\}">C</figure-callout>}}_2{\mathrm{\&epsiv;}}^{\&prime;}+{{\mathrm{<figure-callout\; id="1"\; label="C"\; filenames="A2009101477550016H1.png"\; state="\{\{state\}\}">C</figure-callout>}}_1}^2}}{{\mathrm{<figure-callout\; id="0"\; label="C"\; filenames="A2009101477550016H1.png"\; state="\{\{state\}\}">C</figure-callout>}}_0+C_1{C}_2\frac{C_2({\mathrm{\&epsiv;}}^{\&prime;2}+{\mathrm{\&epsiv;}}^{\&prime;\&prime;2})+{\mathrm{<figure-callout\; id="1"\; label="C"\; filenames="A2009101477550016H1.png"\; state="\{\{state\}\}">C</figure-callout>}}_1{\mathrm{\&epsiv;}}^{\&prime;}}{{{\mathrm{<figure-callout\; id="2"\; label="C"\; filenames="A2009101477550015H1.png,A2009101477550016H1.png"\; state="\{\{state\}\}">C</figure-callout>}}_2}^2({\mathrm{\&epsiv;}}^{\&prime;2}+{\mathrm{\&epsiv;}}^{\&prime;\&prime;2})+2C_1{\mathrm{<figure-callout\; id="2"\; label="C"\; filenames="A2009101477550015H1.png,A2009101477550016H1.png"\; state="\{\{state\}\}">C</figure-callout>}}_2{\mathrm{\&epsiv;}}^{\&prime;}+{{\mathrm{<figure-callout\; id="1"\; label="C"\; filenames="A2009101477550016H1.png"\; state="\{\{state\}\}">C</figure-callout>}}_1}^2}}---\left(34\right)$

$\mathrm{\&psi;}=\frac{a{\mathrm{\&epsiv;}}^{\&prime;\&prime;}-b{\mathrm{\&epsiv;}}^{\&prime;}-b}{c{\mathrm{\&epsiv;}}^{\&prime;}-c-d{\mathrm{\&epsiv;}}^{\&prime;\&prime;}}$

$\mathrm{\&rho;}=\frac{{\mathrm{\&epsiv;}}^{\&prime;}}{b+\frac{{\mathrm{a\&epsiv;}}^{\&prime;\&prime;}-{\mathrm{b\&epsiv;}}^{\&prime;}-b}{{\mathrm{c\&epsiv;}}^{\&prime;}-c-d{\mathrm{\&epsiv;}}^{\&prime;\&prime;}}d}$

Abbreviation obtains:

$\mathrm{\&psi;}=\frac{a\frac{{\mathrm{<figure-callout\; id="0"\; label="C"\; filenames="A2009101477550016H1.png"\; state="\{\{state\}\}">C</figure-callout>}}_0+\frac{1}{{\mathrm{<figure-callout\; id="1"\; label="C"\; filenames="A2009101477550016H1.png"\; state="\{\{state\}\}">C</figure-callout>}}_1}}{2\mathrm{\&pi;<figure-callout\; id="1"\; label="f\; C"\; filenames="A2009101477550016H1.png"\; state="\{\{state\}\}">f</figure-callout>}{C_{}}^{}{{}_1}^2{C}_2}[\frac{1}{2\mathrm{\&pi;fQL}}-G]-b\frac{1}{C_1{C}_2}\left\{({\mathrm{<figure-callout\; id="0"\; label="C"\; filenames="A2009101477550016H1.png"\; state="\{\{state\}\}">C</figure-callout>}}_0+\frac{1}{C_1})\right[{\mathrm{<figure-callout\; id="0"\; label="C"\; filenames="A2009101477550016H1.png"\; state="\{\{state\}\}">C</figure-callout>}}_0+C_1-\frac{1}{{\left(2\mathrm{\&pi;f}\right)}^{2}L}]-{{\mathrm{<figure-callout\; id="1"\; label="C"\; filenames="A2009101477550016H1.png"\; state="\{\{state\}\}">C</figure-callout>}}_1}^2\}-b}{c\frac{1}{C_1{\mathrm{<figure-callout\; id="2"\; label="C"\; filenames="A2009101477550015H1.png,A2009101477550016H1.png"\; state="\{\{state\}\}">C</figure-callout>}}_2}\frac{1}{C_1{C}_2}\left\{({\mathrm{<figure-callout\; id="0"\; label="C"\; filenames="A2009101477550016H1.png"\; state="\{\{state\}\}">C</figure-callout>}}_0+\frac{1}{C_1})\right[{\mathrm{<figure-callout\; id="0"\; label="C"\; filenames="A2009101477550016H1.png"\; state="\{\{state\}\}">C</figure-callout>}}_0+C_1-\frac{1}{{\left(2\mathrm{\&pi;f}\right)}^{2}L}]-{{\mathrm{<figure-callout\; id="1"\; label="C"\; filenames="A2009101477550016H1.png"\; state="\{\{state\}\}">C</figure-callout>}}_1}^2\}-c-\mathrm{<figure-callout\; id="0"\; label="d\; C"\; filenames="A2009101477550016H1.png"\; state="\{\{state\}\}">d</figure-callout>}\frac{C_{}}{}\frac{{}_0+\frac{1}{{\mathrm{<figure-callout\; id="1"\; label="C"\; filenames="A2009101477550016H1.png"\; state="\{\{state\}\}">C</figure-callout>}}_1}}{2\mathrm{\&pi;<figure-callout\; id="1"\; label="f\; C"\; filenames="A2009101477550016H1.png"\; state="\{\{state\}\}">f</figure-callout>}{C_{}}^{}{{}_1}^2{C}_2}[\frac{1}{2\mathrm{\&pi;fQL}}-G]}$

$\mathrm{\&rho;}=\frac{\frac{C_0+\frac{1}{C_1}}{2\mathrm{\&pi;f}{C_1}^2{C}_2}[\frac{1}{2\mathrm{\&pi;fQL}}-G]}{b+\frac{a\frac{C_0+\frac{1}{C_1}}{2\mathrm{\&pi;f}{C_1}^2{C}_2}[\frac{1}{2\mathrm{\&pi;fQL}}-G]-b\frac{1}{C_1{C}_2}\left\{(C_0+\frac{1}{C_1})\right[C_0+C_1-\frac{1}{{\left(2\mathrm{\&pi;f}\right)}^{2}L}]-{C_1}^2\}-b}{c\frac{1}{C_1{C}_2}\frac{1}{C_1{C}_2}\left\{(C_0+\frac{1}{C_1})\right[C_0+C_1-\frac{1}{{\left(2\mathrm{\&pi;f}\right)}^{2}L}]-{C_1}^2\}-c-d\frac{C_0+\frac{1}{C_1}}{2\mathrm{\&pi;f}{C_1}^2{C}_2}[\frac{1}{2\mathrm{\&pi;fQL}}-G]}}$ By above-mentioned two formula, can try to achieve material moisture and density respectively, in solution procedure, both can not interfere with each other.The constant a that its result of calculation is only determined with pure dried material and pure water specific inductive capacity, b, c, d, and the parameters C in the resonator sensor equivalent model ₀, C ₁, C ₂, L, G also has detection limit resonance frequency f relevant with quality factor q.

5.3PLL frequency resolution and measuring accuracy relationship analysis

For the turbine oil that contains trace water, moisture content is the granule Discrete Distribution or exists with the molecular group form in oil, so mixing material is very little to the loss of microwave, the ε in the specific inductive capacity _r' be far longer than imaginary part ε _r", so the effective dielectric constant of mixing material can calculate with following formula:

${{\mathrm{\&epsiv;}}_{\mathrm{egr}}}^{\&prime;}={{\mathrm{\&epsiv;}}_{\mathrm{or}}}^{\&prime;}[1+3\frac{{{\mathrm{\&epsiv;}}_{\mathrm{wr}}}^{\&prime;}-{{\mathrm{\&epsiv;}}_{\mathrm{or}}}^{\&prime;}}{({\mathrm{\&epsiv;}}_{\mathrm{wr}}^{\&prime;}+2{\mathrm{\&epsiv;}}_{\mathrm{or}}^{\&prime;})-V_r({\mathrm{\&epsiv;}}_{\mathrm{wr}}^{\&prime;}-{\mathrm{\&epsiv;}}_{\mathrm{or}}^{\&prime;})}{V}_r]---\left(35\right)$

ε ' _Egr, ε ' _Wr, ε ' _OrBe respectively the relative dielectric constant of moisture turbine oil, the relative dielectric constant of water and the relative dielectric constant of turbine oil; V _rBe water shared volume share in turbine oil.The content of steam turbine W/O is less than per mille generally speaking, V _r1, and following formula can be similar to and be written as:

${{\mathrm{\&epsiv;}}_{\mathrm{egr}}}^{\&prime;}={{\mathrm{\&epsiv;}}_{\mathrm{or}}}^{\&prime;}[1+3\frac{{{\mathrm{\&epsiv;}}_{\mathrm{wr}}}^{\&prime;}-{{\mathrm{\&epsiv;}}_{\mathrm{or}}}^{\&prime;}}{({\mathrm{\&epsiv;}}_{\mathrm{wr}}^{\&prime;}+2{\mathrm{\&epsiv;}}_{\mathrm{or}}^{\&prime;})}{V}_r]---\left(36\right)$

Because little water turbine oil is very little to the loss of microwave, so available ε ' _EgrReplace ε _Egr, with (36) formula substitution (34) formula put in order turbine oil water percentage and resonator cavity frequency deviation relation:

$V_r=\frac{1}{3B{{\mathrm{\&epsiv;}}_{\mathrm{or}}}^{\&prime;}}[(1-{{\mathrm{\&epsiv;}}_{\mathrm{or}}}^{\&prime;})-2\frac{\mathrm{\&Delta;f}}{f_0}]---\left(37\right)$

In the formula, coefficient $B=\frac{{\mathrm{\&epsiv;}}_{\mathrm{wr}}^{\&prime;}-{\mathrm{\&epsiv;}}_{\mathrm{or}}^{\&prime;}}{{\mathrm{\&epsiv;}}_{\mathrm{wr}}^{\&prime;}+2{\mathrm{\&epsiv;}}_{\mathrm{or}}^{\&prime;}}.$ By measuring relative frequency deviation (the δ f/f of turbine oil by resonator cavity ₀), can determine the water percentage V in the turbine oil _r(volumetric water content).

If when pure turbine oil passed through resonator cavity, the relative frequency deviation that causes was (δ f/f ₀),, the turbine oil that contains micro-moisture by the time relative frequency deviation that causes be (δ f ₀₁/ f ₀), so the relative frequency deviation difference that causes when containing the turbine oil of micro-moisture and pure turbine oil by resonator cavity is:

$\frac{\mathrm{\&Delta;}\left(\mathrm{\&delta;f}\right)}{{\mathrm{<figure-callout\; id="0"\; label="f"\; filenames="A2009101477550016H1.png"\; state="\{\{state\}\}">f</figure-callout>}}_0}=\frac{{\mathrm{\&delta;f}}_0}{f_0}-\frac{{\mathrm{\&delta;f}}_{01}}{f_0}---\left(38\right)$

With the pass of turbine oil water percentage be:

$V_r=\frac{1}{{3\mathrm{B\&epsiv;}}_{\mathrm{or}}^{\&prime;}}\frac{\mathrm{\&Delta;}\left(\mathrm{\&delta;f}\right)}{f_0}---\left(39\right)$

As seen from Figure 2, micro-water content measuring accuracy and frequency resolution are linear relationships.As can be seen from Table 1 if desired the micro-water content measuring accuracy reach 100,000/, frequency accuracy need can be realized less than 608.37KHz so, considers the frequency reference crystal oscillator frequency, the frequency resolution of PLL is 500KHz.

The relation of table 1 micro-water content measuring accuracy and frequency resolution

Frequency resolution (KHz)	??60.837	??304.185	??486.7	??608.37	??3041.9
						The micro-water content measuring accuracy	??1×10 -6	??5×10 -6	??8×10 -6	??1×10 -5	??5×10 -5

5.4 system works flow process

1. when system started working, by core controller FPGA10 control PLL and the predetermined frequency of VCO output, frequency step was 100KHz.

2. the frequency from voltage controlled oscillator 4 inputs inputs to resonator cavity through circulator 3.

3. the frequency sweep input signal enters resonator cavity 1 through circulator 3 by Waveguide-microbelt conversion equipment 2.

4. when signal inputed to resonator cavity, the signal of resonator cavity output passed through Waveguide-microbelt conversion equipment 2 equally, passes through circulator 3 again, exported detector diode 7 to and carried out envelope detection, and the envelope of output is being sampled through entering ADC behind the amplifier 8.

5. when input signal was resonance frequency, resonator cavity began resonance, and electric field energy is converted into the magnetic field energy maximum, and therefore the signal amplitude of output has maximum decay.

6. when input signal was resonance frequency, FPGA10 can detect the tangible changes in amplitude of ADC9, stops frequency sweep, and output frequency is fixed on resonance frequency.

7. input to frequency mixer from another road of power splitter and carry out down signals and sample, obtain resonance frequency by ADC9.

8.FPGA10 with resonance frequency, the data transmission of temperature sensor and pressure transducer is calculated liquid water content in the turbine oil to DSP11.

9. the turbine oil liquid water content data transmission of calculating is returned FPGA10, show by display device again, simultaneously, sample frequency, the data transmission of temperature sensor and pressure transducer to host computer is handled, and perhaps debugs on host computer by the DSP11 emulator and shows.

Signal Processing and key control unit software workflow are as shown in Figure 3

Claims (2)

1. micro-water content test system based on resonant cavity perturbation method, based on the perturbation of resonator cavity, promptly this principle of skew takes place with dielectric change in dielectric constant in the chamber in the resonance frequency of resonator cavity.Under uniform temp, pressure, because the specific inductive capacity of steam turbine oil and water is different, the specific inductive capacity of different its mixed solutions of water cut is also just different in the turbine oil, when the steam turbine oil that contains moisture passes through microwave cavity, its resonance frequency will be offset, and side-play amount is different and different with the water percentage in the turbine oil, therefore can determine what of micro-water content in the steam turbine oil by the side-play amount of measuring the resonator cavity resonance frequency.Native system is filled the resonant frequency point and the Q value of resonator cavity down, relative dielectric Changshu of anhydrous oil by measuring anhydrous oil; Using the same method to record the relative dielectric Changshu that contains little water oil, and contrast anhydrous oil and little water oil phase can obtain the micro-water content of oil to dielectric Changshu and in conjunction with the lumped parameter of resonator cavity.Realized a micro-water content test system based on resonant cavity perturbation method based on this principle, native system can be applied in the micro-water content measurement in petroleum industry and water conservancy field.

2. micro-water content test system based on resonant cavity perturbation method as claimed in claim 1, it is characterized in that, resonant frequency point and Q value that Resonant-cavity Method test micro-water content need be tested resonator cavity, traditional way is to control the signal of voltage-controlled oscillator (VCO) output certain frequency by a DC voltage, with this signal de-energisation resonator cavity, owing to have uncertain relation between VCO control voltage and the output frequency, can not obtain accurate VCO frequency by control voltage, native system will be tested the power and the frequency of resonator cavity coupling output terminal output signal, measurement for power can realize by power detector, if micro-water content is ten thousand in the turbine oil/or when lower, then to arrive hundreds of hertz even tens hertz, increase technical difficulty the measuring accuracy of VCO output signal frequency.System has proposed a kind of scheme of frequency precognition, this scheme adopts constant temperature with reference to crystal oscillator and phaselocked loop (PLL skill) art, can realize the output of less step frequency signal, primary controller can be according to measurement process control PLL, the VCO output frequency is set on the Frequency point that needs, thereby in Q value measuring process, do not need to carry out the measurement of frequency, this scheme can measure exactly resonator cavity have carry and the no-load situation under the Q value.This system has saved the module of frequency measurement, greatly reduces the technical difficulty of system, has reduced cost.

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